Shrinking the ACL

Abstract & Commentary

Synopsis: Thermal treatment of partial ACL tears was successful in restoring stability in carefully selected patients.

Source: Indelli PF, et al. Monopolar thermal treatment of symptomatic anterior cruciate ligament instability. Clin Orthop. 2003;407:139-147.

Standard treatment of functionally unstable knees with partial ruptures of the ACL has been either nonoperative or ACL reconstruction surgery. Studies reporting on thermal ACL treatment are limited. The purpose of this study is to present the short-term results of ACL insufficient knees that are functionally unstable but in continuity. Twenty-eight consecutive partial ACL or ACL reconstruction failures were treated with thermal "shrinkage" with a monopolar device and were followed for a minimum of 2 years. All ACL injuries were less that 6 months old, and KT-1000 differences at 134 N in the anterior-posterior direction were > 6 mm. Further documentation at arthroscopy showed an incomplete tear defined as > 7 mm of intact ACL at the minimum cross-sectional area after thermal treatment and intact ligament origins and insertions. KT-1000, IKDC scores, and return-to-sport activities were used to measure outcomes. Postoperative rehabilitation included nonweight bearing in a locked brace and increased to progressive knee range of motion at 2-6 weeks.

The IKDC outcomes were nearly normal in 96% of the patients, and KT-1000 side-to-side differences were on average 1.9 mm in 26 of the 28 knees. One failure was noted at 8 weeks and resulted in ACL reconstruction. Indelli and colleagues concluded that ACL shrinkage seems to be an alternative to ACL reconstruction in selected patients.

Comment by James R. Slauterbeck, MD

Thermal denaturation of collagen in the ACL had not been reported in large numbers. The idea appears attractive, but few guidelines exist, and treatment, technique, outcomes measures, and rehabilitation protocols are not commonplace. At this stage, much of the science and surgical indications behind ACL denaturation has been borrowed from the literature surrounding capsular shrinkage in shoulders.

Although this study does not provide any basic science information as to the quality of the ACL or the graft tissue, the strength of the article is that strict inclusion criteria were adhered to, operative details provided, and postoperative protocols followed. However, a comparative group of nonoperatively treated ACL-deficient patients or ACL-reconstructed patients would have been a nice addition to the paper.

I am overall intrigued by this article. I have performed several ACL "denaturations" and have been happy with my short-term results. I have been tempted to apply thermal energy to partial ACL ruptures in several other cases but was not sure of the potential adverse or successful outcomes. I have been concerned that the thermal shrinkage would mostly treat the surface of the ACL and not penetrate the depths of the injured tissues. Additionally, I have been concerned about potential stiffness from limited motion and weight bearing postoperatively. This article alleviates some of my anxieties. I will be looking for some basic science articles in this area defining the mechanical and geometric characteristics of the treated ACL and will await longer-term follow-up before performing this procedure on a large scale. However, in selected moderately athletic individuals, I will be less hesitant to consider this treatment.

Dr. Slauterbeck is Associate Professor, Department of Orthopaedic Surgery, Texas Tech University Health Sciences Center, Albuquerque, NM